I just started a new job running an ICP-OES. I am having trouble with my results for MO and the calculations for dilution.
I had previously calibrated with a purchased 500ml bottle of Mo standard at 100PPM. We have an in-house base material that is dissolved as a check standard. Up to this point, it always came in around 0.53% to 0.56%.
A new lot of Mo standard was opened and all subsequent results dropped to 0.46% to 0.50%. I dissolved a NIST iron chip standard with 4390PPM Mo. Diluted to 500ml brings it to 8.78%. I created a method and calibrated with the NIST standard and all my results were good.
1.) Is the 100PPM vs. the 8.78PPM the reason for this?
2.) HOW do I calculate the PPM needed for 3.0% max. Mo.